Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–2.5
A strong, 1.5-2.5 foot thick slab on top of weak snow at the base of the snowpack remains our primary concern. This structure exists on most upper-elevation slopes and on some (E-N-W) mid-elevation slopes. This weak snow will be obvious to identify on more shaded slopes and be more difficult to see on more sunny slopes where it presents as facets on top of a melt-freeze crust.
Over the past 3 weeks of dry weather, obvious signs of instability have decreased, as have your chances of triggering one of these avalanches. While they've become more stubborn, they still can be triggered. Tracks on a slope, or another party member crossing a slope without incident does not mean you will be as lucky.
A prolonged drought has caused the strong slab to facet and weaken, losing its structure and cohesion in some locations. In others, it is alive, well, and disconcertingly solid (see video at right/below). This makes evaluating the slope you are on for yourself, and continuing to make assessments as you travel vital to moving safely through the mountains. Scroll down to the Forecast Discussion for more details.